PatchTableContents.cs

public class PatchTableContents : MonoBehaviour
{
    public IEnumerator Start()
    {
        // Load the table. 
        var table = LocalizationSettings.StringDatabase.GetTableAsync("My Table");
        yield return table;

        // Prevent the table from being unloaded and the changes lost.
        Addressables.ResourceManager.Acquire(table);

        // Apply our changes
        var stringTable = table.Result;
        var entry = stringTable.GetEntry("Some Entry");
        entry.Value = "Hello World";

        // Create a new entry
        var newEntry = stringTable.AddEntry("New Entry", "Localized Value");
    }
}